1. Field of the Invention
The present invention relates to a vehicle drive assist system that sets risks for white lines and three-dimensional objects existing around a vehicle and detected, for example, by a stereo camera, a monocular camera, or a millimeter-wave radar and that controls steering or braking so that the vehicle can take an optimum route.
2. Description of the Related Art
In recent years, various technologies of improving safety of a vehicle have been developed and practically used. In these technologies, a traveling environment in front of the vehicle is detected, for example, by a camera or a laser radar mounted in the vehicle. On the basis of data on the traveling environment, obstacles and a preceding vehicle are recognized, and alerting, automatic braking, and automatic steering are performed.
For example, in a technology disclosed in Japanese Unexamined Patent Application Publication No. 2004-110346, an obstacle existing around a vehicle is detected, and the current risk potential of the vehicle to the obstacle is calculated. On the basis of the risk potential, the operation of vehicle equipment is controlled so as to urge the driver to perform a driving operation concerning the motion of the vehicle in the front-rear and right-left  directions. The operation of the vehicle equipment is controlled in only one of the front-rear direction and the right-left direction.
However, the control disclosed in the above publication is performed strictly in accordance with the current risk potential, and therefore, cannot effectively respond to the risk that varies with movements of the vehicle and the obstacle. In other words, even in a path that is considered optimal at present, the risk will frequently increase in the future.